TULSA, OK — Department of Energy-funded research has resulted in the commercialization of an innovative technology designed to bolster supplies of two of America’s most critical natural resources: natural gas and water.
The technology, developed by Drake Engineering of Helena, MT, helps producers of coalbed natural gas (CBNG) clean up co-produced water for beneficial uses, in turn addressing critical water shortages in the U.S. West. Such research answers President Bush’s call for expanding domestic oil and gas production while protecting the environment.
CBNG is the hottest natural gas play in the United States—and the fastest-growing new source of water typically co-produced with oil and gas. Estimates vary, but at least 15,000 CBNG wells have been drilled just in the Powder River Basin of Wyoming and Montana, site of the most intense CBNG drilling activity.
As coal is formed underground, methane is trapped within the coal. Coalbeds also are natural aquifers, and the water in coalbeds sustains pressure that keeps the methane adsorbed to the coal. In order to produce CBNG, it is necessary to pump this water to the surface to lower the pressure in the coalbed reservoirs, thus stimulating the release of methane. The methane produced from coalbeds can be added to natural gas pipelines without special treatment.
This relatively simple, low-risk method commonly used to produce natural gas from coalbeds is the source of both promise and concern for the arid West’s water resources.
The promise lies in the scope of the resource. America’s economically recoverable reserves of CBNG total an estimated 100 trillion cubic feet—more than half the Nation’s total of proved conventional natural gas reserves. Because coalbed resources are well-known in this country, exploration risk is minimal. And CBNG resources are usually shallow, which keeps drilling costs low.
However, concerns over CBNG produced water presents unique challenges for recovering this resource. Some landowners and environmental groups worry that the CBNG produced water used in irrigation or discharged onto the land could alter the soil’s structure and chemistry—a particular concern for crop irrigation.
If the public and regulators perceive a significant threat to groundwater quality from CBNG produced water, operators could be forced to choose between expensively treating water from these typically low-volume gas wells and shutting them in, costing the Nation an important source of gas supply and the West critically needed water. If rendered suitable, CBNG produced water could help Western states solve their perennial problem of water shortages.
Drake Engineering’s new water-treatment process is an outgrowth of a project in which researchers at Montana State University are evaluating phytoremediation of CBNG produced water. This entails selecting wetlands plant species identified for their natural filtering capabilities and using them in artificial or modified natural wetlands. The plants naturally reduce the levels and negative effects of salts in CBNG produced water so that it can be discharged safely to surface land or waters.
Through a project subcontract, Drake Engineering designed and developed a prototype of a lab-tested fluid-bed resin exchange treatment system for removing sodium from CBNG produced water. Drake since has patented and begun commercializing the process by field-testing it in Powder River Basin CBNG operations. Equipment leasing contracts already are being issued.
The project was funded by the Office of Fossil Energy's National Energy Technology Laboratory (NETL) Office of Petroleum, which places a major emphasis on produced-water treatment and management options as a way to reduce costs and improve environmental protection.